Creep PMMA ANSYS 13.0

[faisal]

Hi all,

i am now trying to observe the temperature-dependent Creep effect of PMMA ( Plexiglas XT from Evonik ) under (one, constant) high temperature (forming temperature), using ANSYS. i need the engineeering data of any available PMMA because apparently the data provided by Evonik is not enough for the simulation. could anyone help me with the data needed for simulation?

this my be related or not, but some extra detail about the simulation: PMMA rest on some kind of block and should deform because it's own weight (gravity?) without the influence of any other outside forces. i am using static structural analysis.

i am sorry for my (non proper) english and thanks in advance

faisal

[Jorgen]

I suspect that you will not be able to find the necessary experimental data in the literature. I would be happy, however, to run the necessary experimental tests and calibrate a suitable ANSYS creep model for a fee.

As a side note, the MCalibration software can now calibrate any built-in material model in ANSYS Mechanical (including all creep models). I will announce this new capability soon...

Jorgen

[faisal]

hi jorgen,

as a student, it is almost impossible for me to pay a high fee for the data. i would like, however, to know the quotation.

is there experimental data for other type of material(not necessarily pmma) for creep simulation that i can get from anywhere?

another question, is it the right to use static structural analysis for this? because i've tried explicit dynamic and i am quite satisfied with the initial result i've got. though it is not the full simualition that i desire ( change of shape in high temperature:temperature condition cant be put in explicit dynamic, it seems )

[Jorgen]

To test a thermoplastic material for material model calibration requires multiple experimental tests. There are a number of testing labs that can do those experiments, and the fee is more than $1,000 (just to mention a number). I can provide a precise quotation is needed.

If you are a student then perhaps you should probably run the experiments your self.

I recommend a static structural analysis for creep simulations since you are interested in long times. You may be able to use an explicit dynamic model but that will likely be less accurate.

-Jorgen

[faisal]

hallo jorgen,

i am interested in having the precise quotation, and if possible, a simplified explanation or outline of the experiment taht should be done to obtain the needed data for the simulation. In any case, thank you.

about the simulation: i somehow got some data (very rough) of a PMMA in form of stress-strain graph on 115°C. i recreate the graph in Material Data in ANSYS (roughly) and tried to do the simulation. the following is roughly information of the simulation

-static structural
-a fixed support on the block
-a pressure of 100 kPa on the plate
-contact: type-Frictionless ; contact: PMMA Plate-surface; target: block-surface
-mesh: automatic

but the programm is unable to solve it. may anyone help me and give me insight of what i did wrong here?
the error information is given in german, roughly translated:
- the value limit is surpassed, maybe caused by the value of the load or insufficient support
- the Solver-Pivot-Warning was given during Solution process. this may be caused by badly conditioned Matrix of material properties, not enough definition of model or contact problem.

is it not enough to have stress-strain data? or are there other problems too?